/*
* Copyright (c) 2006-2009 Erin Catto http://www.box2d.org
*
* This software is provided 'as-is', without any express or implied
* warranty.  In no event will the authors be held liable for any damages
* arising from the use of this software.
* Permission is granted to anyone to use this software for any purpose,
* including commercial applications, and to alter it and redistribute it
* freely, subject to the following restrictions:
* 1. The origin of this software must not be misrepresented; you must not
* claim that you wrote the original software. If you use this software
* in a product, an acknowledgment in the product documentation would be
* appreciated but is not required.
* 2. Altered source versions must be plainly marked as such, and must not be
* misrepresented as being the original software.
* 3. This notice may not be removed or altered from any source distribution.
*/

#include <Box2D/Common/b2StackAllocator.h>
#include <Box2D/Common/b2Math.h>

b2StackAllocator::b2StackAllocator()
{
    m_index = 0;
    m_allocation = 0;
    m_maxAllocation = 0;
    m_entryCount = 0;
}

b2StackAllocator::~b2StackAllocator()
{
    b2Assert(m_index == 0);
    b2Assert(m_entryCount == 0);
}

void* b2StackAllocator::Allocate(int32 size)
{
    b2Assert(m_entryCount < b2_maxStackEntries);

    b2StackEntry* entry = m_entries + m_entryCount;
    entry->size = size;
    if (m_index + size > b2_stackSize)
    {
        entry->data = (char*)b2Alloc(size);
        entry->usedMalloc = true;
    }
    else
    {
        entry->data = m_data + m_index;
        entry->usedMalloc = false;
        m_index += size;
    }

    m_allocation += size;
    m_maxAllocation = b2Max(m_maxAllocation, m_allocation);
    ++m_entryCount;

    return entry->data;
}

void b2StackAllocator::Free(void* p)
{
    b2Assert(m_entryCount > 0);
    b2StackEntry* entry = m_entries + m_entryCount - 1;
    b2Assert(p == entry->data);
    if (entry->usedMalloc)
    {
        b2Free(p);
    }
    else
    {
        m_index -= entry->size;
    }
    m_allocation -= entry->size;
    --m_entryCount;

    p = NULL;
}

int32 b2StackAllocator::GetMaxAllocation() const
{
    return m_maxAllocation;
}
